1. Field of the Invention
Drum type mowers as exemplified in the prior U.S. Pat. No. 3,391,522 to Zweegers are very popular for cutting hay because they provide effective cutting and simultaneous windrowing of the cut hay without substantial auxiliary mechanisms. Such drum mowers are so identified because they employ a vertically disposed cylindrical member which resembles a drum. The bottom of the drum is equipped with a relatively large diameter collar or disc. It is customary to have a plurality of hay cutting blades radially projecting at arcuately spaced apart positions from beneath the large diameter disc. The blades rotate concurrently with the unitary drum and disc to effect hay harvesting. The drums, or rotors as they are often referred to, are used in pairs which are arranged to rotate inwardly toward each other. As the hay is cut it falls on the enlarged discs and is delivered rearwardly of the mower in the confined space between the cooperative pair of drums.
The present invention is concerned with the blades used in drum mowers and more particularly with blades which may yield upon the striking of an obstruction without being damaged and which will automatically resume their cutting positions when the obstruction is passed.
2. Description of the Prior Art
A patent search was conducted and the following U.S. Pat. Nos. were believed to be pertinent to the patentability of the device of this invention.
Walker--2,707,859 PA1 Klein, Jr.--2,762,188 PA1 Wenzel et al--3,190,064 PA1 Dunlap et al--3,208,209 PA1 Wixson--3,303,637 PA1 Zweegers--3,389,539 PA1 Zweegers--3,391,522 PA1 Zweegers--3,443,369 PA1 Huff et al--3,444,674 PA1 Van Der Lely--3,550,360 PA1 Geist et al--3,708,967 PA1 Kasberger--3,735,572 PA1 Moss et al--4,058,959 PA1 Inada--4,086,700 PA1 Ballas et al--4,112,653 PA1 Fisher et al--4,126,990 PA1 Mathews--4,160,356 PA1 Owens--4,170,099
The three patents to Zweegers and the patents to Van Der Lely, Kasberger, and Mathews (applicant's own prior patent) all depict drum type mowers with radially projecting cutting blades.
The patents to Walker, Klein, Jr., Dunlap et al, Wixson, Moss et al, Inada and Owens all disclose the use of flexible spring wire as mower cutting blades. Owens states his mowing flails could be made of wire cables or Nylon filaments. The Klein, Jr. grass cutting wire is held tautly at both ends when operating. Dunlap shows a variety of embodiments of wire blades. Wixson employs a flexible spring wire as the cutting blade on a rotary mower in which the wire is used in a loop form with both ends attached to a rotating disc. Moss et al shows a mower blade formed of spring wire and arranged in a special loop with two abutting ends acting as the radially extending grass cutting blade and having an auxiliary wire blade abutting the two ends but attached to the rotating member at a spaced apart position. The patent to Inada shows a mower cutting head in which flexible wire members are used as the cutters.
The Geist patented mower employs non-metallic lines as the grass cutting elements. Huff et al discloses a fence cleaner using flails of fan belt material. Ballas et al shows a mower using a plurality of flexible non-metallic cords projecting radially outwardly from a disc to effect grass cutting. Fisher employs Nylon pins to effect grass cutting. Wenzel et al shows a mower having hinged flail cutting blades which are not made of wire.
It is apparent from the above brief synopses of the prior art patents that the use of flexible spring wires as mower cutting blades is quite old. However, applicant's spring wire blades are relatively rigid and could not be described as flexible in the manner of the flexible blades of the prior art described above. It is applicant's use of "L" shaped spring wire blades with each such blade having a fixed attachment only at the upper end of the vertical leg of the blade to the rotating drum element that applicant contends is new and patentable. The vertical leg acts as a torsional spring about which the blade can yield when striking an immovable obstruction. There is nothing in the prior art patents to suggest applicant's employment of an L-shaped spring wire blade operating in a drum type mower as set forth herein.